Eat foods that have high calorie content but are still healthy and nutritious. Whole grains, avocados, nuts, potatoes, lean meats and fish are healthy options that are high in calories, nutritious, add weight and sustain the body during workouts.

At every meal and snack, add extra calories. Add wheat germ or powdered milk to casseroles and cereal. Add avocados, olives and fruit to salads and sandwiches. Eat hard boiled eggs as a side to every meal for extra protein. A common way to add calories is mixing meat to pasta. Add sausage, ground beef or ground turkey to pasta sauces or use as a topping. Pasta and meat provides great mix of carbs and the essential weight-gaining nutrient protein.

Eat at consistent times every day. Do not eat past six o'clock in the evening. At night, the body's metabolism slows down and does not burn off the sugar that foods you eat produce. If it's not burned off, the body stores this sugar as fat. Fat cells like to build up in the belly area because typically this area does not have a high concentration of muscle mass. Do not skip meals. Set a reminder on your phone or make a schedule of meals. Planning ahead will also give you the opportunity to meal plan and calorie count. Eat three meals a day along with two snacks.

Double the amount of protein and carbohydrates you consume during meals. Increasing your portion size will help you gain weight and feed your muscles the protein they need to grow and rebuild after a workout. Consuming protein rather than junk food will help prevent stomach fat from accumulating. Protein is mostly acids that do not contain sugar or are broken down into sugar. Sugar turns into fat. Your body will produce less fat when you consume mostly protein in your diet. Slow down when you eat to avoid indigestion.

Use a supplement containing creatine. Creatine allows the muscles to absorb water and lets the muscles recover more rapidly by being able to work out longer and rebuild faster. Add creatine to protein shakes or mix with whole milk to enhance performance and stamina. When the muscles absorb water and recover they become heavier and rebuild larger. Combined with core exercises, creatine will help abdominal muscles become more defined and burn any existing stomach fat.